Case studies of coupling between the E and F regions during unstable sporadic-E conditions -: art. no. 1447

[1] Simultaneous F-region airglow, E-region coherent-scatter radar, and ionosonde observations were made in Greece during the summer sporadic-E season in 2002. In this paper we report on two case studies during which patchy sporadic-E layers were accompanied by midlatitude spread F, coherent VHF radar echoes (including two-stream echoes), and traveling ionospheric disturbances registered by the airglow instrument. We argue that these events give strong evidence that polarization electric fields are built up in the E region and are mapped upward to the F region, creating rising and falling regions in the bottomside plasma. The resulting structure creates conditions for midlatitude spread F, as detected by the ionosonde. This correlation between patchy sporadic E and midlatitude spread F is further supported in a companion paper. Upward coupling of this sort is particularly efficient in regions of F-region plasma uplift and airglow depletion, since the F-region Pedersen conductivity is low which reduces the electrical load on the E-region generator.